Integrated electrical circuits and other microstructured components are conventionally produced by applying a plurality of structured layers onto a suitable substrate which, for example, may be a silicon wafer. In order to structure the layers, they can be first covered with a photoresist which is sensitive to light of a particular wavelength, for example 248 nm, 193 nm or 157 nm. The wafer coated in this way can be subsequently exposed in a projection exposure apparatus. During the exposure, a pattern of structures on a mask can be projected onto the photoresist with the aid of a projection objective. Since the imaging scale is generally less than 1, such projection objectives are often referred to as reduction objectives.
After the photoresist has been developed, the wafer can be subjected to an etching process so that the layer becomes structured according to the pattern on the mask. The photoresist still remaining can then be removed from the other parts of the layer. This process can repeated until all the layers have been applied on the wafer.